Causier B, Ashworth M, Guo W, Davies B

Transcription factors activate or repress target gene expression, or switch between activation and repression. In animals and yeast, Groucho/Tup1 co-repressor proteins are recruited by diverse transcription factors to induce context-specific transcriptional repression. Two groups of Gro/Tup1-like co-repressors have been described in plants. LEUNIG (LUG) and LEUNIG_HOMOLOG (LUH) constitute one group ...

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and TOPLESS (TPL) and the four TPL-related (TPR) co-repressors form the other. To discover the processes in which the TPL and TPR co-repressors operate, high-throughput yeast two-hybrid approaches were used to identify interacting proteins. We found that TPL/TPR co-repressors predominantly interact directly with specific transcription factors, many of which were previously implicated in transcriptional repression. The interacting transcription factors reveal that the TPL/TPR family has been co-opted multiple times to modulate gene expression in diverse processes, including hormone signaling, stress responses, and the control of flowering time, for which we also show biological validation. The interaction data suggests novel mechanisms for the involvement of TPL/TPR co-repressors in auxin and jasmonic acid signaling. A number of short repression domain (RD) sequences have previously been identified in Arabidopsis (Arabidopsis thaliana) transcription factors. All known RD sequences were enriched amongst the TPL/TPR interactors, and novel TPL-RD interactions identified. We show that the presence of RD sequences is essential for TPL/TPR recruitment. This data provides a framework for TPL/TPR-dependent transcriptional repression. It allows for predictions about new repressive transcription factors, co-repressor interactions and repression mechanisms and identifies the wide range of plant processes that utilize TPL/TPR-mediated gene repression.

Date: Nov. 07, 2011

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